Emerging therapies in metastatic bone pain

Introduction: Current treatment for metastatic bone pain is mainly palliative. Recent insights into the molecular mechanisms involved in bone metastases have led to the identification of promising therapeutic targets. This review offers an update of preclinical and clinical data on new drugs for metastatic bone pain. Areas covered: Biphosphonates are the gold standard of bone-targeted therapy in bone metastases, for their anti-resorptive and analgesic effects. New drugs aim at breaking the 'vicious cycle' of bone metastatic disease, due to the bidirectional interaction between cancer cells and bone microenvironment. Osteoprotegerin, RANK/RANKL interaction, cathepsin K, the Wnt/beta-catenin pathway and sclerostin are emerging targets for modulation of cancer-induced bone desorption. Other promising targets are those expressed in cancer cells that metastasize to bone, including Src, nerve growth factor, endothelin A, TGF-beta and CXCR4. Interesting therapeutic options include targets on nociceptors that innervate the bone, such as TPRV1, Trk and cannabinoid receptors. Expert opinion: Emerging therapies promise, in the next 10 years, a significant expansion in the array of therapeutic options for bone metastases. Most of these drugs are still in an early phase of development. Further clinical trials are needed to support the evidence of their efficacy and tolerability profile.